(1) Field of the Invention
The present invention relates to a porcelain enamel frit for sheet iron ground coat which does not contain fluorine or a fluorine compound.
(2) Description of the Prior Art
Conventional porcelain enamel frits for sheet iron ground very often contain fluorine and fluorine compounds. The reason is as follows. Fluorine or fluorine compounds act as a flux in the production of porcelain enamel frit for sheet iron ground coat to promote the smelting of the raw material mixture, they act as a low melting point compound to lower the firing temperature at the firing for enameling, and they act to give a good gloss to the resulting porcelain enamel. However, fluorine or fluorine compounds are very toxic and volatilize in air from frit during the frit making and the firing for enameling. Therefore the use of porcelain enamel frit containing fluorine or fluorine compound is not preferable in view of public nuisance.